We continue to study placental proteins as cancer markers. The pregnancy-specific beta1 glycoprotein (SP1) is produced by normal human fibroblasts but does not appear to be a useful marker in cases of fibrosarcoma, osteogenic sarcoma, glioma or breast carcinoma. Placental protein 5 is also made by human fibroblasts in vitro but its regulation by the cell appears to be different from that of SP1. Chemical modification of SP1 is being explored in an attempt to understand its unusual CD spectrum. Placental lactogen (PL) is made by different cells of a testicular choriocarcinoma than is alpha subunit. Large forms of PL have been detected in serum and placenta at term, even when blood and tissue have been rapidly processed. Analysis of oligosaccharides released from CG-alpha by trifluoroacetolysis has revealed heterogeneity unrecognized in current structural formulas of this glycoprotein. HeLa cells make alpha subunit in serum-free media with growth factor supplementation, at rates up to 80 percent of those in standard medium containing fetal calf serum.